Presently, EP printers that are capable of reproducing color images tend to employ organic photoconductor (OPC) belts, with plural developer stations arrayed along the OPC belt's travel path. Each developer module is associated with a mechanism that enables it to engage the OPC belt so as apply a liquid color toner to image-exposed regions on the OPC belt. Such an EP color printer requires a belt tensioning mechanism and a belt position sensor to assure proper orientation of the belt in relation to a scanned laser beam writing station.
Image transfer from an OPC belt is generally via an image transfer roller/pressure roller combination which is selectively brought into engagement with the OPC belt once the belt has been fully toned with cyan (C) , magenta (M), yellow (Y) and black (K) toning solutions. As known to those skilled in the art, a color EP printer employing an OPC belt requires four complete revolutions of the belt through the developer stations so that each developer station can be independently operated to apply its particular color toner to the OPC belt surface. Some EP color printers transfer an applied toner to a media sheet after each individual color toner is deposited on the OPC belt, while others superimpose the color toners on previously toned areas of the belt so as to achieve a full color image on the OPC belt. The fully toned image is then transferred to a media sheet in a single step.
Such color EP printers thus employ many parts for moving various portions of the printer into and out of engagement with the OPC belt. Each separate operating mechanism adds cost to the EP printer and is a source of potential malfunction.
Accordingly, it is an object of this invention to provide an EP printer with a simplified mechanism for enabling engagement between an image transfer roller mechanism and a photoconductor surface.
It is another object of this invention to provide an improved EP printer wherein the same mechanism that enables movement of an image transfer roller further controls engagement and disengagement of liquid toner developer modules.
It is yet another object of this invention to provide a color EP printer wherein a single actuating mechanism enables engagement of each of a plurality of color developer modules with a drum-shaped photoconductor surface.